Light microscopy, transmission electron microscopy and scanning electron microscopy combined with computer assisted morphometry will be used to clarify tissue changes in the pars scleralis region of the monkey optic nerve head induced by elevation of intraocular pressure. Axoplasmic transport markers including tritiated amino acids and horseradish peroxidase will be utilized to document and further define nerve injury in the monkey. Complimentary studies in monkeys, and human autopsy eye tissues using scanning electron microscopy and a variety of axon staining techniques will also be performed. Computer assisted morphometric measurements of axonal and glial tissue elements and mitochrondrial distribution in the monkey optic nerve will be performed to considerably refine the definition of pressure-induced nerve injury, with regard both to location and pathogenesis. Direct measurements of tissue pressure in several levels of the nerve head will also be made to further correlate pressure changes with morphologic alterations in nerve tissues.